The electrical machine is usually embodied as a starter/generator and/or as an electrical drive. As a generator it enables a recuperation of the brake energy, i.e. the kinetic energy of the vehicle is transformed by the generator into electric energy which is then stored. The function of the electrical machine as a starter makes it possible to start the combustion engine. Use of the electrical machine as an additional drive provides an additional torque, e.g. to accelerate the vehicle or for the pure electrical drive of the vehicle. Furthermore, hybrid vehicles comprise at least one electronics arrangement for controlling the energy flow and an energy storage device.
The energy storage device consists of a series connection of energy storage cells and of further electronic components. The energy storage cells are usually installed together with the control electronics in a closed housing inside the vehicle. For dissipating gases possibly escaping from the energy storage cells the housing is provided with a defined opening or leakage. Due to the high powers of an electrical machine in a hybrid drive a high lost heat to be dissipated is produced among others in the energy storage device, which lost heat is systematically transported outwards via heat exchangers, which are installed between the energy storage cells, and/or is dissipated by circulating air.
It is disadvantageous with such an embodiment that in particular when mounting the energy storage device outside of the passenger compartment, in the event of a failure it turns out to be difficult to dissipate the gases escaping from the energy storage cells, since on the one hand here high demands are exacted to the tightness of the housing, in order to keep soil and humidity away from the battery cells, and on the other hand the housing must comprise a certain leakage for gas dissipation and/or for dissipation of possibly arising condensation water. The demanded tightness contradicts the demanded dissipation of unwanted gases or liquids.
A further disadvantage is the previously usual arrangement of the heat exchangers between the energy storage cells for dissipating the lost heat, as it is shown e.g. in DE 90 11 893 U1. The volume of the energy storage device is increased by such an arrangement, what is unwanted due to the continuously increasing lack of space in particular when installing it into a motor vehicle. Renouncing of these heat exchangers and a cooling exclusively by circulating air, however, is out of question due to the high lost heat in the energy storage cells and the air cooling insufficient for this purpose.